A measuring device of this type is shown in German Patent No. DE 195 20 488 C1, in which the gas to be measured flows into a hollow guide, which is used as a measuring section, and wherein the absorption of infrared radiation by the gas to be detected is, in general, an indicator of the concentration of that gas. The drawback of this prior-art measuring device is the fact that the intensity at the site of the radiation-sensitive detectors may become very low depending on the number of curvatures in the hollow guide.